1. Field of the Invention
The present invention relates to a micro switch, and particularly, to a micro switch having an excellent capability of opening contacts for a direct current and being capable of rapidly extinguishing an arc.
2. Background of the Invention
A micro switch denotes a compact switch which converts a physical force into a driving force for switching an electric switch on or off so as to switch internal contacts on or off. Such micro switch is widely being used as a source for generating an electric signal indicating an operation of a mechanical device at a specific position. Further, it allows contacts to be fast switched on or off, and accordingly it is also used to control a current supply to an electric load device utilized in a electric power equipments.
The micro switch utilized in the electric power equipments is typically capable of being switched on or off to conduct or cut off a direct current with maximum voltage of 250 volts (hereinafter, referred to as ‘V’) and maximum current of 16 ampere (hereinafter, referred to as ‘A’), for example.
However, the related art micro switch just has a short separated distance (i.e., open distance) between its internally disposed movable contact and stationary contact (e.g., a normally open contact or normally closed contact) upon an opening operation, and also is not equipped with any member for fast extinguishing an arc generated between the movable contact and the stationary contact upon the opening operation. Accordingly, the related art micro switch may be switched on or off so as to conduct or cut off a direct current with 250V voltage and 0.3 A current, for example. That is, a direct current level which can be conducted or cut off is drastically decreased. For a cycle of alternating current having a period (time interval) with a plus (+) value, a time point with zero (0) current and a period (time interval) with a minus (−) value, the micro switch is switched off (opened) at the time point where a current becomes zero (0) (i.e., zero (0) point), so as to cut off (block) a relatively great alternating current. However, the direct current does not have the zero point, and thereby an amount of direct current which can be cut off by switching the micro switch off may drastically be decreased.
Contrast to this, a circuit breaker of electric power equipments uses a motor as a driving source for charging its internal trip spring. Here, in case of constructing a control circuit including such motor and a magnetic contactor for controlling driving/stopping of the motor, such construction requires a micro switch capable of cutting off a direct current with higher than 250V voltage and 1.0 A current, for example.
However, the related art micro switch has too short open distance (e.g., about 1 millimeter) between the movable contact and the stationary contact, thereby merely cutting off a less amount of direct current. As a result, the micro switch is not appropriate to be used for controlling an operation of a motor installed in electric power equipment.
Furthermore, since the related art micro switch is not equipped with a member for fast extinguishing an arc generated between the movable contact and the stationary contact when the movable contact is separated from the stationary contact, it cannot effectively cut off a great direct current. Accordingly, when a great direct current is generated, the motor disposed at a rear side of the micro switch may be damaged as well as the micro switch. In addition, it is impossible to charge a trip spring of a breaker, whereby the breaker may not be operable.